JP2013516042A - Ignition and pressure measuring device for internal combustion engine - Google Patents

Abstract

  The present invention relates to an ignition and pressure measuring device having a spark plug (2), the spark plug (2) being attached to the outer body (14), the outer body (14) and having a signal output terminal (38). A pressure sensor (34) and a support tube (4) supporting the electronic means (44) for processing said signals, which are permanently connected to the upper end of the outer body, and on the one hand an output terminal of the pressure sensor (38), on the other hand, is provided with a conductive element (46) attached to the input terminal of the electronic processor means (44) and a metal shell (6) surrounding the lower end, the electronic processor means and the pressure sensor. The shell has operating means (60) for attaching the device to the cylinder head and is attached to the outer body of the spark plug at the lower end. .

Description

  The present invention relates to an ignition and pressure measuring device for an internal combustion engine.

  In an internal combustion engine, it is effective to know the pressure in the cylinder. In particular, this allows better control of the combustion in the engine. Thereby, fuel consumption and pollutants discharged can be reduced. In a so-called gasoline engine, the pressure sensor for measuring the pressure in the cylinder eliminates the necessity of providing an engine knock sensor.

  That is, it is known to attach a pressure sensor to a spark plug. Commonly used pressure sensors are based on the piezoelectric effect. As is known, spark plugs conventionally have a central electrode, a ground electrode, an insulator core, and an outer body, also known as a spark plug shell. Furthermore, the pressure sensor is attached to the outside of the outer body of the spark plug. When a spark plug is attached to the cylinder head of an operating engine, the pressure in the corresponding cylinder stresses the insulator core in a direction opposite to the preload of the piezoelectric sensor due to combustion occurring in this cylinder. This force associated with the combustion occurring in the cylinder tends to move the insulator core longitudinally by moving the insulator core away from the cylinder so that the outer body is elastically deformed, This reduces the force applied to the preloaded piezoelectric sensor. Such a change in the force applied to the sensor generates an electrical signal that is a function of the pressure in the cylinder. This signal is very sensitive to mechanical and electromagnetic disturbances. Therefore, signal transmission from the sensor's sensitive element to the electronic device that processes the signal must be done carefully.

  French Patent No. 2926933 describes a spark plug associated with a force sensor and a connecting device. The force sensor is arranged in a conventional manner around one end of the outer body of the spark plug. The connecting device has a flexible cap for accommodating this end of the spark plug. The flexible cap supports electronic processor means for signals transmitted by the force sensor and resilient electrical contacts connected to the processor means. The force sensor has a connector pin electrode designed to fit into an elastic electrical contact supported by a flexible cap. In order to facilitate the positioning of the pins in the elastic electrical contacts, the connection device is provided with means for preventing erroneous operation. Furthermore, the flexible cap has a central hole in which a spring is housed for connection between the high voltage terminal of the coil and the power rod of the spark plug center electrode. The connecting device further includes a metal shell, and a flexible cap is disposed in the metal shell. The metal shell has a resilient tab at the free end on the side facing the spark plug to allow electrical contact with the outer body of the spark plug, thereby grounding the metal shell.

  The inventor has discovered that for this device, the signal received by the processor means is sometimes of insufficient quality to derive sufficiently reliable and accurate pressure information.

  The object of the present invention is to overcome said drawbacks by providing a device having a spark plug and a pressure sensor adapted to provide more reliable information about the pressure in the engine cylinder. Preferably, the device is also adapted to provide more accurate pressure information.

To this end, the present invention is an ignition and pressure measuring device comprising a spark plug having an outer body and a pressure sensor attached to the outer body of the spark plug, the pressure sensor comprising: Provided is an ignition and pressure measuring device having a signal output terminal, a support tube supporting electronic means for processing the signal, and a metal shell surrounding the support tube, the electronic processor means and the pressure sensor. . The device according to the invention comprises:
A support tube is permanently connected to one end of the outer body, called the upper end, which houses the pressure sensor;
A conductive element is attached on the one hand to the output terminal of the pressure sensor and on the other hand to the input terminal of the electronic processor means;
One end of the metal shell, called the lower end, is attached to the outer body of the spark plug,
The metal shell has operating means for attaching the device to a cylinder head of an internal combustion engine.

  In another aspect, the ignition and pressure measurement device according to the present invention is an integrated assembly integrating ignition, in-cylinder pressure measurement, measurement data processing, vibration damping due to increased inertia (described in the following section). Assembled at the factory to form. There is no removable connection between the pressure sensor and the electronic processor means, both elements being directly connected by a conductive element. As a result, the signal transmission between the pressure sensor and the electronic processor means is assured of high quality no matter what mechanical stresses and vibrations the device according to the invention experiences. Furthermore, the attachment of the device to the cylinder head is carried out in a single operation thanks to the operating means provided on the metal shell (in contrast to the known devices, this requires at least two operations. It had been).

  Also, the fact that the metal shell is attached to the outer body of the spark plug according to the present invention has the following fundamental essential advantages. The metal shell increases the inertia and stiffness of the rigid assembly formed by the outer body of the spark plug and the metal shell. As a result, the natural frequency of the outer body thus provided with the metal shell is lower than the natural frequency of only the outer body. That is, attaching a metal shell to the outer body of the spark plug shifts the natural frequency of the outer body so that it deviates from the band of the pressure sensor. Furthermore, the inertia and stiffness provided by the metal shell limits the outer body distortion that tends to occur under the cylinder head distortion transmitted to the outer body at the seat. Thus, the pressure sensor is quite insensitive to vibrations and stresses experienced by the spark plug. As a result, the signal / noise ratio obtained is very good and is significantly increased compared to the ratio obtained with previously known devices.

  Finally, the operating device is formed on the outer body of the spark plug in all previously known devices, whereas the presence of the operating means in the metal shell facilitates the mounting of the device of the invention on the cylinder head. To. This is because the operating means is now moved outside the cylinder head. Furthermore, this arrangement can provide a more compact device. That is, the axial dimension of the portion of the spark plug protruding beyond the metal shell is reduced (because it no longer has an operating means), and the operating means is integrated into the metal shell without increasing the axial dimension. Has been.

  Preferably, these operating means have a hexagonal cross section.

  Advantageously, the operating means is formed at one end of the shell, called the upper end, opposite the lower end. Therefore, these operating means are easily accessible regardless of how deep the device of the invention is located. In short, this means that the diameter of the shell in the region of the support tube and the processor electronics is larger than the wrench opening of the operating means (the diameter between the sides in the case of hexagons), and furthermore the maximum outer diameter of the operating means (six It is possible to use a shell that is larger than the diameter between the vertices of the square.

  Advantageously, the lower end of the metal shell extends adjacent to the seat of the spark plug, thereby forming a stop when the device is attached to the cylinder head.

  Advantageously, the metal shell is attached to the outer body of the spark plug by means of a weld provided around its entire circumference. This ensures a seal between the spark plug and the metal shell, which protects the pressure sensor and the electronic processor means from the aggressive environment and moisture of the cylinder.

  Preferably, at least one O-ring is arranged between the support tube and the metal shell near the upper end.

  Alternatively or preferably in combination, the electronic processor means are embedded or encapsulated in an insulating material. Such embedding or encapsulation protects the electronic processor means from potential contaminants that can penetrate the metal shell. In addition, if the metal shell is used as a mold and the encapsulant fills the empty space between the support tube and the metal shell, it can occur between the support tube and the metal shell and affect the electronic processor means. Vibrations that can be avoided are avoided.

  Advantageously, the ignition and pressure measuring device is further arranged between the insulator core and the support tube of the spark plug along a portion of the support tube that extends at least beyond the electronic processor means to the outer body of the spark plug. Having a shielded sleeve. This shielding sleeve protects the signals transmitted by the pressure sensor (not yet processed) and the electronic processor means from electromagnetic interference caused by the high voltage lines described below.

The invention also relates to an assembly comprising on the one hand an ignition and pressure measuring device according to the invention and on the other hand a connecting device,
A high voltage line for supplying power to the center electrode of the spark plug is provided, said high voltage line, on the one hand, passing through the support tube and being engaged with the insulator core of the spark plug On the other hand, it has a connector for connecting the high voltage line to the high voltage output terminal of the coil converter,
A coupling element connected on the one hand to the connector of the ignition and pressure measuring device connected to the output terminal of the electronic processor means and located near the upper end of the metal shell, on the other hand to the signal input terminal of the coil transformer Is provided.

  As a result of the simplicity of such a device, it is possible to provide connecting devices with various lengths at a lower cost (here "length" means when both devices are assembled) The dimensions of the connecting device along the axial direction of the ignition and pressure measuring device). That is, the length of the connecting device may be selected with respect to the depth of the cylinder head recess to which the ignition and pressure measuring device is attached. Therefore, it is no longer necessary to develop various sized ignition and pressure measuring devices to meet all market needs. This is because one device with a compact design is suitable for various types of cylinder heads.

  Further details and advantages of the present invention will become apparent from the following description of preferred embodiments, given by way of example only, with reference to the accompanying schematic drawings.

1 is a schematic view of an ignition and pressure measuring device according to the present invention. FIG. 2 is a schematic view of the device of FIG. 1 in combination with a connection device, with a portion of the metal shell and a portion of the support tube shown in cross section. FIG. 3 is an exploded perspective view of the apparatus shown in FIG. 2.

  1 to 3 show an ignition and pressure measuring device according to the invention, which has in particular a spark plug 2, a support tube 4 and a metal shell 6, which form an integral assembly. ing.

  Conventionally, the spark plug 2 has a center electrode 8, a ground electrode 10, an insulator core 12, and an outer body 14, also known as a spark plug shell.

  The spark plug 2 generates a spark in the combustion chamber of the internal combustion engine. This spark is generated between two electrodes, that is, the center electrode 8 and the ground electrode 10. The center electrode 8 is attached to the inside of the insulator core at one end of the insulator core 12. A high voltage current is supplied to the center electrode through a high voltage line described below.

  An insulator core 12, generally made of ceramic, is mounted within the outer body 14. The outer body 14 has a generally tubular shape with a circular cross section. The lower end portion of the outer body 14 supports the ground electrode 10. The ground electrode 10 faces the center electrode 8. The insulator core 12 is positioned in the outer body 14 and is held in the outer body 14 by crimping. The upper end portion 16 (see FIG. 3) of the outer body 14 is bent so as to cover the shoulder portion of the insulator core 12 in order to crimp the insulator 12.

  The outer peripheral surface of the spark plug outer body 14 has, on the electrode side, a threaded portion 18 for screwing the device according to the invention into a cylinder head (not shown). Above the threaded portion 18, the outer body 14 has a flange 20, and the lower surface 22 of this flange, called the seat, acts as a stopper when the device is screwed into the cylinder head. Above the flange 20, the outer body 14 has a substantially cylindrical upper portion 32 to which a force sensor 34 is attached.

  The force sensor 34 shown here is of the piezoelectric type and has a piezoelectric element that constitutes a sensitive element of the sensor mounted between two electrodes 24 and 28. The upper side of the flange 20 of the outer body 14 serves as a support for the electrode 24. Since this electrode 24 is in contact with the outer body 14 screwed into the cylinder head, it is grounded. As a result, this electrode 24 is also called a ground electrode 24. The electrode 28 receives an electrical signal transmitted by the piezoelectric element subjected to the stress change. This electrode is referred to herein as the output electrode 28 of the force sensor. In addition to the piezoelectric element 26 and the electrodes 24 and 28, the force sensor 34 further includes an insulator washer 30.

  The force sensor 34 is mechanically preloaded by a ring 40 called a preload ring. The shape of the ring 40 is adapted to the shape of the upper portion 32 of the outer body 14. The ring 40 extends from the force sensor 30 to approximately the crimping region and is welded to the outer body 14.

  The output electrode 28 of the force sensor has a tab 38 that extends in the axial direction and forms an output terminal 38 of the force sensor, and an electrical signal from the piezoelectric element 26 is transmitted through the tab 38. The insulator washer 30 itself has an insulating tab 36 extending axially (radially) in the output terminal 38 to electrically insulate the output terminal 38 from the preload ring 40. Since the preload ring 40 is attached to the outer body 14, it is grounded.

  As mentioned above, the device according to the invention further comprises a support tube 4. The support tube 4 is made of an electrically insulating material such as a synthetic polymer material. The support tube 4 has an enlarged region 26 at the lower end portion, and the support tube is connected to the upper end portion of the outer body 14 of the spark plug and the force sensor 34 by the enlarged region. An axial lower surface 72 of the support tube is brought into contact with the shoulder portion of the preload ring 40.

  The support tube 4 has at least one recess 42 on its outer peripheral surface (having a plurality of recesses in the illustrated example), and these recesses are provided with electronic processor means (electronic calculation). A housing for accommodating the processing means 44 is formed. The electronic processor means 44 includes, for example, an electronic board with an application specific integrated circuit, also known as an ASIC. These printed boards perform, for example, amplification and filtering of a signal transmitted by the force sensor 34 and conversion of the analog signal into a digital signal (A / D converter). However, it is alternatively possible to provide the electronic processor means 44 with only one amplifier stage.

  In accordance with the present invention, the electronic processor means 44 is connected directly to the force sensor 34 via a conductive element 46. The conductive element 46 is supported by the support tube 4. In the illustrated example, the conductive element 46 is a rigid flat plate having an S-shaped profile. Alternatively, the conductive element 46 can be a flexible wire. This conductive element 46 is permanently attached, for example by welding, to the output terminal 38 of the force sensor on the one hand and to the input terminal of the electronic processor means 44 on the other hand. Therefore, no connector is interposed between the force sensor 34 and the electronic processor means 44.

  At the output, the electronic processor means 44 is connected via a flat cable or other conductive element supported by the support tube 4 to a female ring connector 50 having three coaxial ring contacts ( The contact is not shown in the drawing because it is formed inside the ring connector 50). The support tube 4 has an enlarged diameter region 64 in the upper portion, and the ring connector 50 is completely accommodated in the enlarged diameter region 64. Since the electronic processor means 44 is disposed outside the support tube 4, a hole for allowing the flat cable to pass therethrough is formed through the shoulder portion of the tube in which the enlarged diameter region 64 is formed. Further, an O-ring 66 is disposed between the ring connector 50 and the support tube 4 adjacent to the upper side 70 in the axial direction of the support tube.

  The ignition and pressure measuring device according to the invention is adapted to be connected to the connection device shown in FIGS. 2 and 3 for connection to a coil transformer. The connection device has a coupling element 52 and a high voltage line 54.

  The coupling element 52 has on one side a ring-shaped male connector with a coaxial ring-shaped contact that is inserted into the ring-shaped connector 50 of the ignition and pressure measuring device. On the other side, the coupling element 52 has at least one plug 53 that allows connection to the signal input terminal of the coil transformer. The processed signal sent to the transformer passes through the transformer by cable or other conductive means for transmission to the on-board computer.

  The high voltage line 54 of the connecting device makes it possible to supply the spark plug with the power provided by the high voltage coil of the transformer. The high voltage line 54 has a conductive rod 58. In the assembled state, the rod 58 supports a coupling element 52 having a tubular shape. The rod 58 passes through the support tube 4. Thus, the lower end portion of the rod 58 is inserted into the insulator core 12 of the spark plug so as to be in contact with the center electrode 8. In order to ensure electrical continuity between the rod 58 and the center electrode 8, the insulator core may be provided with a conductive spring or any other known suitable means. At the upper end of the rod 58, a connector 56 is provided for connecting the high voltage line 54 to a high voltage output terminal (not shown) of the coil transformer.

  As mentioned above, the ignition and pressure measuring device according to the invention also has a metal shell 6. The metal shell 6 entirely surrounds the support tube 4, the elements supported by the support tube 4, and the force sensor 34. The metal shell 6 has a substantially cylindrical tubular main part with circular inner and outer cross-sections and an upper part with a smaller length forming the operating means 60 with a hexagonal cross-section.

  According to the present invention, the shape of the lower end 61 of the metal shell is adapted to the shape of the flange 20 of the outer body 14 of the spark plug. In particular, the inner diameter of the shell on the lower side in the axial direction is substantially the same as the outer diameter of the flange 20 (within the range of the mounting gap). This lower end 61 of the metal shell 6 is welded to the outer body 14 of the spark plug. In the illustrated example, a weld bead 62 is formed over the entire circumference of the metal shell between the lower side in the axial direction of the metal shell and the flange 20 of the outer body 14. Preferably, such welding is performed by a laser. The weld bead 62 thus formed satisfies at least the following three functions.

  The weld bead 62 integrates the metal shell 6 with the outer body 14 thereby strengthening the assembly. The inertia provided by the shell reduces the natural frequency of the outer body of the spark plug well below the band of the force sensor 34 and can occur under vibration and distortion of the cylinder head. Reduce distortion. This improves the signal / noise ratio. The resulting ignition and pressure measuring device provides an extremely reliable and accurate measurement.

  The weld bead 62 ensures the grounding of the metal shell 6 (because the shell 6 is in contact with the outer body 14 and the outer body 14 itself is in contact with the cylinder head). Thereby, the metal shell 6 protects the entire electronics (force sensors and electronic processor means, etc.) from ambient electromagnetic disturbances. Once amplified, the signal is less susceptible to electromagnetic disturbances and thus provides specific shielding outside the ignition and pressure measuring device for the delivery of the amplified and / or filtered and / or converted signal It is not necessary to do.

  The weld bead 62 provides liquid and air tightness between the metal shell 6 and the outer body 14. Thereby, the metal shell 6 protects the entire electronics from any chemical attack by the environment.

  It should be noted that the lower axial side of the metal shell is welded to the metal body 14 adjacent to the body seat 22. This configuration is possible because the operation region 60 for operating the apparatus is formed in the metal shell 6. As a result, the ignition and pressure measuring device according to the invention is very compact. The spark plug 2 without operating means has a reduced axial dimension. The electronic processor means is located as close to the force sensor as possible, facing the protruding part of the insulator core 12.

  In the illustrated example, the operation region 60 is formed at the upper end of the metal shell 6 and protrudes from the support tube 4 in the axial direction. This operating area 60 forms a peripheral wall that surrounds one or more plugs 53 of the coupling element 52 when the connecting device is assembled with the ignition and pressure measuring device according to the invention. Yes. When connecting a coil transformer to the connecting device, this peripheral wall is involved in guiding the transformer signal input terminal towards the corresponding plug 53.

  The outer diameter of the support tube 4 in the enlarged diameter region 64, particularly in the axial upper side 70, is substantially the same as the inner diameter of the main part of the metal shell 6 (within the range of the mounting gap). On the other hand, the operating area 60 of the shell has a minimum inner diameter that is smaller than the outer diameter of the axially upper side 70 of the support tube. The transition between the main cylindrical part of the shell and the operating area 60 thereby forms an inner shoulder that serves as a stop for the support tube 4 (the support tube is further connected to the preload ring 40). Abut). An O-ring 68 is disposed between the support tube 4 and the metal shell 6. This ring is disposed in a groove formed in the enlarged diameter region 64 of the support tube.

  The illustrated ignition and pressure measuring device also has a first shielding sleeve 76 which is a protruding portion of the insulator core 12 (an insulator core protruding from the outer body 14). ). This shielding sleeve protects the raw signal carried by the conductive element 56 and the electronic processor means 44 from electromagnetic disturbances generated by a high voltage line supplying electrodes to the spark plug. The shielding sleeve may be formed from metal, whether solid or perforated, or may be formed by metallization of the outer peripheral surface of the insulator core 12.

  In the example shown, a second shielding sleeve is provided between the high voltage line, in particular the rod 58 and the coupling element 52 of the connecting device. This shielding sleeve may be formed by metallization inside the coupling element 52 or by a metal cladding.

  The present invention includes various modifications made to the illustrated embodiments, and these modifications are within the scope of the appended claims.

  In particular, the present invention is not limited to piezoelectric force sensor type pressure sensors. The pressure sensor may be implemented by any other known means, such as one or more strain gauges disposed on the outer body of the spark plug.

Claims (10)

An ignition and pressure measuring device comprising a spark plug (2), the spark plug (2) being attached to an outer body (14) and an outer body (14) of the spark plug and a signal output terminal A pressure sensor (34) having (38), a support tube (4) supporting electronic means (44) for processing said signal, and a metal tube surrounding said support tube, electronic processor means and pressure sensor. In the type having (6),
A support tube (4) is permanently connected to one end of the outer body (14), called the upper end, which houses the pressure sensor (34);
A conductive element (46) is attached on the one hand to the output terminal (38) of the pressure sensor and on the other hand to the input terminal of the electronic processor means (44),
One end (61) of the metal shell, called the lower end, is attached to the outer body (14) of the spark plug;
Ignition and pressure measuring device, characterized in that the metal shell (6) has operating means (60) for attaching the device to a cylinder head of an internal combustion engine.   2. The device according to claim 1, wherein the operating means (60) has a hexagonal cross section.   The device according to claim 1 or 2, wherein the operating means (60) is formed at one end of the shell, called the upper end, opposite the lower end (61).   The lower end (61) of the metal shell extends adjacent to the seat (22) of the spark plug and forms a stopper when the device is attached to the cylinder head. A device according to claim 1.   A metal shell (6) is attached to the outer body (14) of the spark plug by welding (62) over the entire circumference of the outer body (14). apparatus.   The at least one O-ring (66) is arranged between the support tube (4) and the metal shell (6) near the upper end of the metal shell (6). The apparatus of any one of Claims.   7. A device according to any one of the preceding claims, wherein the electronic processor means (44) is embedded or encapsulated in an insulator material.   Along the portion of the support tube that extends between the insulator core (12) of the spark plug and the support tube (4), at least beyond the electronic processor means (44) to the outer body (14) of the spark plug, 8. A device according to any one of the preceding claims, wherein a shielding sleeve (76) is arranged. In an assembly comprising, on the one hand, an ignition and pressure measuring device according to any one of claims 1 to 8, and on the other hand a connecting device,
In the connection device,
A high voltage line (54) is provided for supplying power to the center electrode (8) of the spark plug, which on the one hand passes through the support tube (4) and is an insulator of the spark plug. A conductive rod (58) engaged with the core (12), on the other hand, a connector (56) for connection to the high voltage output terminal of the coil transformer;
A coupling element (52) is provided, which on the one hand is connected to the output terminal of the electronic processor means (44) and is located near the upper end of the metal shell (6). An assembly characterized in that it is adapted to be connected to a connector (50) of the ignition and pressure measuring device, on the other hand, to the signal input terminal of the coil transformer.   The assembly according to claim 9, wherein the connecting device comprises a shielding sleeve (74) between the rod (58) of the high voltage line (54) and the coupling element (52).

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